1. Field of the Invention
The present invention falls within the field of municipal solid waste (MSW) landfill barrier systems. It relates to a MSW landfill barrier system, and in particular, to a MSW landfill barrier system capable of prolonging breakthrough time of leachate and a manufacturing method thereof.
2. Description of Related Art
The production of municipal solid waste (MSW) rapidly increases with the progressive urbanization and continuous improvement of people's living standards in China. Nowadays, the annual production volume of MSW in China has been 240 million tons and is still rapidly increasing at a rate of 8% to 15% each year, topping the world in either the production volume or the increasing rate thereof. Large amounts of solid waste directly damage urban security and stability. MSW landfills, with low technology doorsill and large disposal capacity, are the ultimate disposal means and currently one of the main measures for waste handling and disposal, accounting for 90.5% of the total disposal capacity.
The MSW in China contains high content of kitchen waste and high content of water, making it easy to produce high leachate head after dumping and accordingly easy to cause landslides which may damage the urban environment and menace citizens' lives and property. High leachate head may also destroy antifouling barriers and cause an early breakthrough of pollutants, resultantly polluting the surrounding environment of MSW landfills and groundwater. Once the underground environment has been destroyed, it will be tremendously difficult to restore it and bring about incalculable serious consequences.
For landfill barrier systems, the Ministry of Housing and Urban-Rural Development of People's Republic of China has issued “Household Waste Sanitary Landfill Barrier System Engineering Technical Specifications CJJ113-2007”, providing that a double-layer liner structure shall be sequentially stacked from top to bottom as the follow: a leachate collection and removal layer, a main infiltration proof layer (containing liner materials and protective materials), a leakage detection layer, a sub infiltration proof layer (containing liner materials and protective materials), a liner foundation and a groundwater collection and removal layer. In the double-layer liner structure, it shall be able to timely detect the perviousness of the main infiltration proof layer by the leakage detection layer.
Currently, the two HDPE (high-density polyethylene) geomembrane layers, respectively located at top and bottom of the double-layer liner structure, tend to become aging and porous. Under a high leachate head, once the HDPE geomembrane has been destroyed or broken down by pollutants, the leachate will soon reach the lower compacted clay liner and breakthrough the compacted clay liner to seriously threaten the underground environment. There are two prior arts for preventing landfill leachate from breakthrough the barrier system. The first one is to modify the clay liner by mixing additives therein to enhance the clay intensity and improve the clay imperviousness. The second one is to lay geosynthetics and bagged soil protection layer on the basis of the HDPE geomembrane infiltration proof layer so as to enhance the protection of HDPE geomembrane. The first prior art involves complex operation to make it time consuming and labor intensive and thus is inaccessible to industrialization. The second prior art, though having enhanced the protection for HDPE geomembrane, is unable to improve the anti-seepage performance and yet also time consuming and labor intensive.